| 摘要 |
PURPOSE:To select an optional terminal and to attain the mutual call between two sets of transmitter-receiver which are capable of automatic switching between transmission and reception, by using the transmitter-receiver at one side in a call mode and then the one at the other side in an answer mode respectively and furthermore adding a terminal setting means and a terminal selecting means. CONSTITUTION:The operation of a telephone receiver is detected and the detection signal is impressed to a control circuit 21, and the circuit 21 produces the signal corresponding to the operated key and supplies it to the 1st transmitter-receiver 22a as a modulation signal after the operation of a terminal selecting part 25. While the sound signal demodulated by another transmitter-receiver 22b is amplified by an amplifier 10 via a signal changeover switch 23 and drives a speaker 11. If the detection signal is given from a detector 26, the circuit 21 puts the 2nd transmitter-receiver 22b under a transmission state. Thus the sound signal sent from a microphone 1 is amplified by an amplifier 2 and impressed to the transmitter-receiver 22b via an adder 20. Then the FM modulation wave of the 2nd frequency obtained through the FM modulation of the sound signal is sent onto a power supply line L via a transmission transformer 4b and capacitors 5 and 6. |
